Method and apparatus for depositing LED organic film

ABSTRACT

In one embodiment the disclosure relates to an apparatus for depositing an organic material on a substrate, including a source heater for heating organic particles to form suspended organic particles; a transport stream for delivering the suspended organic particles to a discharge nozzle, the discharge nozzle having a plurality of micro-pores, the micro-pores providing a conduit for passage of the suspended organic particles; and a nozzle heater for pulsatingly heating the micro-pores nozzle to discharge the suspended organic particles from the discharge nozzle.

The disclosure claims the filing-date priority to the ProvisionalApplication No. 60/629,312, filed Nov. 19, 2004, the specification ofwhich is incorporated herein in its entirety.

BACKGROUND

The disclosure relates to a method and apparatus for depositing anorganic film on a substrate. Manufacturing light emitting diode (LED)cell requires depositing of two thin organic films on a substrate andcoupling each of the thin films to an electrode. Conventionally, thedeposition step is carried out by evaporating the desired organic filmon the substrate. The film thickness is a prime consideration. The layerthickness is about 100 nm and each layer is optimally deposited to anaccuracy of about ±10 nm. As a result, conventional apparatus formmultiple layers on a substrate with each layer having a thickness ofabout 10 nm. A combination of these layers will form the overall film.Because the organic constituents of the LED are often suspended in asolvent, removing the solvent prior to depositing each layer is crucial.A small amount of solvent in one layer of deposited organic thin filmcan cause contamination and destruction of the adjacent layers.Conventional techniques have failed to address this deficiency.

Another consideration in depositing organic thin films of an LED deviceis placing the films precisely at the desired location. Conventionaltechnologies use shadow masking to form LED films of desiredconfiguration. The shadow masking techniques require placing awell-defined mask over a region of the substrate followed by depositingthe film over the entire substrate. Once deposition is complete, theshadow mask is removed to expose the protected portions of thesubstrate. Since every deposition step starts by forming a shadow maskand ends with removing and discarding the mask, a drawback of shadowmasking technique is inefficiency.

SUMMARY OF THE DISCLOSURE

In one embodiment the disclosure relates to an apparatus for depositingan organic material on a substrate, the apparatus comprising: a sourceheater for heating organic particles to form suspended organicparticles; a transport stream for delivering the suspended organicparticles to a discharge nozzle, the discharge nozzle having a pluralityof micro-pores, the micro-pores providing a conduit for passage of thesuspended organic particles; and a nozzle heater for pulsatingly heatingthe nozzle to discharge the suspended organic particles from thedischarge nozzle.

According to another embodiment, the disclosure relates to a method fordepositing a layer of substantially solvent-free organic material on asubstrate, comprising heating the organic material to form a pluralityof suspended organic particles; delivering the suspended organicparticles to a discharge nozzle, the discharge nozzle having a pluralityof micro-pores for receiving the suspended organic particles; andenergizing the discharge nozzle to pulsatingly eject the suspendedorganic particles from the discharge nozzle. Organic particle mayinclude an organic molecule or a molecular aggregate.

According to another embodiment, the disclosure relates to a method fordepositing a layer of organic material on a substrate. The organicmaterial may be suspended in solvent to provide crystal growth or toconvert an amorphous organic structure into a crystalline structure. Themethod can include heating the organic material to form a plurality ofsuspended organic particles; delivering the suspended organic particlesto a discharge nozzle, the discharge nozzle having a plurality ofmicro-pores for receiving the suspended organic particles; andenergizing the discharge nozzle to pulsatingly eject the suspendedorganic particles from the discharge nozzle. Organic particle mayinclude an organic molecule or a molecular aggregate.

According to still another embodiment, the disclosure relates to anapparatus for depositing an organic compound on a substrate comprising achamber having a reservoir for receiving the organic compound, thechamber having an inlet and an outlet for receiving a transport gas; adischarge nozzle having a plurality of micro-porous conduits forreceiving the organic compound delivered by the transport gas; and anenergy source coupled to the discharge nozzle to provide pulsatingenergy adapted to discharge at least a portion of the organic compoundfrom one of the micro-porous conduits to a substrate.

In yet another embodiment, an apparatus for depositing an organiccompound comprises a chamber having a reservoir for housing the organicmaterial dissolved in a solvent, the reservoir separated from thechamber through an orifice; a discharge nozzle defined by a plurality ofmicro-porous conduits for receiving the organic compound communicatedfrom the reservoir; and an energy source coupled to the discharge nozzleproviding pulsating energy for discharging at least a portion of theorganic compound from one of the micro-porous conduits to a substrate;and a delivery path connecting the chamber and the nozzle. The organiccompound may be substantially free of solvent. Alternatively, theorganic compound may include in solvent. In a solvent-based system, thesolvent discharge from the nozzle provides the added benefit of coolingthe nozzle upon discharge.

In still another embodiment, a micro-porous nozzle for depositing anorganic composition on a substrate includes a thermal sourcecommunicating energy to organic material interposed between the heaterand a porous medium, the porous medium having an integrated mask formedthereon to define a deposition pattern.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a discharge apparatus fordischarging organic compounds, or its mixture, according to oneembodiment of the disclosure;

FIG. 2 is a schematic representation of a discharge apparatus fordischarging organic compounds according to another embodiment of thedisclosure;

FIG. 3 schematically illustrates a discharge nozzle according to oneembodiment of the disclosure;

FIGS. 4A and 4B show an image printed according to one embodiment of thedisclosure;

FIG. 5 is a photoluminescence image of a pattern printed by molecularjet printer system;

FIGS. 6A and 6B show the surface and the cross section, respectively, ofa porous medium; and

FIGS. 7A and 7B illustrate a molecular jet printing apparatus accordingone embodiment of the disclosure in cross-sectional and top views,respectively.

DETAILED DESCRIPTION

In one embodiment, the disclosure relates to a method and apparatus fordepositing a pure organic thin film, or a mixed organic film, or anorganic thin film mixed with inorganic particles, or inorganic thin filmon a substrate. Such films can be used, among others, in the design andconstruction of organic LED.

FIG. 1 is a schematic representation of a discharge apparatus fordischarging organic compounds, or its mixture, according to oneembodiment of the disclosure. Referring to FIG. 1, exemplary apparatusfor deposing an organic material on a substrate includes housing 105having discharge nozzle 125 at one end and a reservoir 107 at anotherend. Reservoir 107 may contain organic constituents required for formingan LED film. The organic constituent may be liquid or solid. Heat source110 is provided to heat reservoir 107 and the content thereof. Heatsource 110 can provide heating of about 100-700° C. In anotherembodiment, the heat source 110 can provide heating of about 300-500° C.

Housing 105 may optionally include inlet 115 and outlet 120. The inletand outlet can be defined by a flange adapted to receive a carrier gas(interchangeably, transport gas.) In one embodiment, the carrier gas isa inert gas such as nitrogen or argon. Delivery path 135 can be formedwithin housing 105 to guide the flow of the carrier gas. Thermal shields160 may be positioned to deflect thermal radiation from hear source 110to thereby protect discharge nozzle 125 and organic particles containedtherein.

In the exemplary embodiment of FIG. 1, the discharge section includesdischarge nozzle 125 and nozzle heater 130. Among others, the dischargenozzle can be formed from anodized porous aluminum oxide or poroussilicon membranes or other solid membranes. Such material are capable ofblocking organic material from escaping through the porous medium whenthe organic material is delivered onto the porous medium's surface.Discharge nozzle 125 includes rigid portions 141 separated bymicro-pores 140. Micro-pores 140 block organic material from escapingthrough the medium until the medium is appropriately activated.Depending on the desired application, micro-pores 140 can provideconduits (or passages) in the order of micro- or nano-pores. In oneembodiment, the pore size is in the range of about 5 nm-500 microns. Inanother embodiment, the pores are about 5 nm-100 nm. In anotherembodiment, the pores are about 100 nm-1 micron. In another embodiment,the pores are about 5 nm-500 microns. In another embodiment pores areabout 100 nm to about 10 microns. Nozzle heater 130 is positionedproximal to the discharge nozzle 125. When activated, nozzle heater 130provides a pulse of energy, for example as heat, to discharge nozzle125. The activation energy of the pulse dislodges organic material 109contained within micro-pores 140.

In a method according to one embodiment of the disclosure, reservoir 107is commissioned with organic material suitable for LED deposition. Theorganic material may be in liquid or solid form. Source heater 110provides heat adequate to evaporate the organic material and formsuspended particles 109. By engaging a carrier gas inlet 115, suspendedparticles 109 are transported through thermal shields 160 towarddischarge nozzle 125. The carrier gas is directed to gas outlet 120through delivery path 135. Particles 109 reaching discharge nozzle arelodged in micro-pores 130. Activating nozzle heater 130 to provideenergy to discharge nozzle 125 can cause ejection of organic particles109 from the discharge nozzle. Nozzle heater 130 can provide energy incyclical pulses. The intensity and the duration of each pulse can bedefined by a controller (not shown.) The activating energy can bethermal energy. A substrate can be positioned immediately adjacent todischarge nozzle 125 to receive the ejected organic particles.Applicants have discovered that the exemplary embodiment shown in FIG. 1can form a think organic film on a substrate with great accuracy. Theembodiment of FIG. 1 is also advantageous in that it can substantiallyreduce substrate heating, minimizes local clogging and provide the mostefficient use of organic material.

FIG. 2 is a schematic representation of a discharge apparatus fordischarging organic compounds according to another embodiment of thedisclosure. Referring to FIG. 2, apparatus 200 is adapted for forming anorganic film substantially free from solvent. Apparatus 200 includesreservoir 210 for receiving organic solution 215. In one embodiment,organic solution 215 contains organic material dissolved in a solvent.Thermal resistor 220 is positioned proximal to reservoir 210 to heatorganic solution 215. Orifice 232 separates reservoir 210 from dischargenozzle 225. Discharge nozzle 225 comprises micro-pores 240 separated byrigid sections 241.

Because of the size of orifice 232, surface tension of organic solutionprevents discharge of organic solution 215 from the reservoir untilappropriately activated. Once thermal resistor 220 is activated, energyin the form of heat causes evaporation of droplet 235 within a chamberof apparatus 200. Solvents have a lower vapor pressure and evaporaterapidly. Once evaporates, organic compound within droplet 235 istransported to discharge nozzle 225. Discharge nozzle 225 receives theorganic material 209 within micro-pores 240. The solvent can be recycledback to organic solution 215 or can be removed from the chamber (notshown). By activating nozzle heater 230, micro-pores 240 dislodgeorganic particles 209, thereby forming a film on an immediately adjacentsubstrate (not shown.) In one embodiment, nozzle heater 230 can beactivated in a pulse-like manner to provide heat to discharge nozzlecyclically.

FIG. 3 schematically illustrates a discharge nozzle according to oneembodiment of the disclosure. In FIG. 3, discharge nozzle 300 comprisesheater 330, porous medium 340 and integrated mask 345. Heater 330 iscommunicates pulse energy in the form of heat to organic material 309causing dislodge thereof from porous medium 340. Integrated mask 345effectively masks portions of the porous medium from transmittingorganic ink material 309. Consequently, a film forming on substrate 360will define a negative image of the integrated mask.

Thus, in one embodiment, the particles can be discharged from the porousmedium by receiving thermal energy from a proximal resistive heater, ora thermal radiation heater, or by electrostatic force pull out of themicro-porous, or by mechanical vibration.

FIGS. 4A and 4B show an image printed according to one embodiment of thedisclosure. Specifically, FIG. 4 shows the printing result using theexemplary apparatus shown in FIG. 3. The ink material is Alq3 and waspre-coated on the backside of an anodized porous alumina disc. FIG. 4Ashows the LED organic printed pattern under halogen illumination. FIG.4B shows the photoluminescence image under UV illumination.

FIG. 5 is a photoluminescence image of a pattern printed by molecularjet printer system according to another embodiment of the disclosure.FIG. 5 was obtained by using the discharge nozzle shown in FIG. 3. Theink material was Alq3. The ink material was drop cast on the backside ofanodized porous alumina disc.

FIGS. 6A and 6B show the surface and the cross section, respectively, ofa porous medium. The porous medium can be used according to theprinciples disclosed herein with a discharge nozzle or as a part of anozzle having an integrated mask (see FIG. 3.) FIG. 6A shows the surfaceof the porous medium. FIG. 6B shows a cross-section of the porousmedium. FIG. 6A shows a scale of 1 μm and FIG. 6B has a scale of 2 μm.

FIGS. 7A and 7B illustrate a molecular jet printing apparatus accordingto an embodiment of the disclosure in cross-sectional and top views,respectively. Referring to FIG. 7A, printing apparatus 700 includesmicro-heater 710 which can be used as a liquid delivery system. Waferbonding layer 715 connects the liquid delivery system to nozzle section720. Porous openings 730 are positioned at a discharge end of nozzle 720and micro-heaters 740 are positioned adjacent to porous openings 730 toproviding energy required to eject organic material or ink from nozzle720. FIG. 7B shows a top view of the nozzle shown in FIG. 7A includingporous openings 730 and heaters 740.

While the principles of the disclosure have been illustrated in relationto the exemplary embodiments shown herein, the principles of thedisclosure are not limited thereto and include any modification,variation or permutation thereof.

What is claimed is:
 1. An apparatus for depositing a thin film of anorganic material on a substrate, the apparatus comprising: a housingdefining a first end and a second end and a plurality of bafflesinterposed therebetween, the housing having an inlet; a reservoircommunicating with the first end of the apparatus, the reservoir storingthe organic material; a discharge nozzle having a plurality ofmicro-pores provided at the second end of the housing; a source heaterheating the organic material to form organic particles that migrate fromthe reservoir to the discharge nozzle; and a pulsing nozzle heaterheating the discharge nozzle for discharging the suspended organicparticles from the discharge nozzle through the micro-pores.
 2. Theapparatus of claim 1, further comprising at least one thermal baffle. 3.The apparatus of claim 1, further comprising a transport stream fordelivering the suspended organic particles to the discharge nozzle,wherein the transport stream is a gas.
 4. The apparatus of claim 3,wherein the transport stream is an inert gas.
 5. The apparatus of claim1, wherein the organic material further comprises a solvent.
 6. Theapparatus of claim 1, wherein the discharge nozzle defines the pluralityof micro-pores separated by a rigid structure.
 7. The apparatus of claim1, wherein the organic material defines a solvent-based composition. 8.The apparatus of claim 1, wherein the organic material defines acomposition having an organic material and an inorganic material.
 9. Anapparatus for depositing an organic material comprising: a housinghaving a micro-porous membrane with a first surface and a second surfaceand a layer of organic particles provided on the first surface of themicro-porous membrane; and a means for supplying pulsing energy to thelayer of organic material provided in the proximity of the first side ofthe micro-porous membrane; wherein the pulsing energy transports theorganic material through the micro-porous membrane from the firstsurface of the micro-porous membrane to the second surface through atleast one baffle.
 10. The apparatus of claim 9, wherein the pulsatingenergy is supplied cyclically.
 11. The apparatus of claim 9, wherein theapparatus is configured to eject said organic particles from the secondsurface.
 12. The apparatus of claim 9, wherein the organic particlesdefine at least one molecule.
 13. The apparatus of claim 9, wherein theorganic particles define a molecular aggregate.
 14. The apparatus ofclaim 9, further comprising a gas transport configured to form a coatinghaving at least one organic particle.
 15. The apparatus of claim 9,further comprising a liquid solvent system configured to form thecoating having at least one organic particle.
 16. The apparatus of claim9, wherein the apparatus is configured to operate in a relative vacuum.17. The apparatus of claim 9, wherein the micro-porous membrane furthercomprises pores of about 5 nm-100 nm.
 18. The apparatus of claim 9,wherein the micro-porous membrane further comprises pores of about 100nm-1 micron.
 19. The apparatus of claim 9, wherein the micro-porousmembrane further comprises pores of about 5 nm-500 micron.
 20. Theapparatus of claim 9, wherein the micro-porous membrane furthercomprises pores of about 100 nm-10 micron.
 21. The apparatus of claim 9,wherein the heater provides pulsing heat about 100-700° C.
 22. Theapparatus of claim 9, wherein the heater provides pulsing heat about300-500° C.
 23. The apparatus of claim 9, wherein means for supplyingpulsing energy is a resistive heater and the pulsing energy is a thermalenergy.
 24. The apparatus of claim 23, wherein the heater is in contactwith the layer of organic material.
 25. The apparatus of claim 9,wherein the pulsing energy is a mechanical vibration energy.